2,412 research outputs found

    Impact wave deposits provide new constraints on the location of the K/T boundary impact

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    All available evidence is consistent with an impact into oceanic crust terminating the Cretaceous Period. Although much of this evidence is incompatible with an endogenic origin, some investigators still feel that a volcanic origin is possible for the Cretaceous/Tertiary (K/T) boundary clay layers. The commonly cited evidence for a large impact stems from delicate clay layers and their components and the impact site has not yet been found. Impact sites have been suggested all over the globe. The impact is felt to have occurred near North America by: the occurrence of a 2 cm thick ejecta layer only at North American locales, the global variation of shocked quartz grain sizes peaking in North America, the global variation of spinel compositions with most refractory compositions occurring in samples from the Pacific region and possibly uniquely severe plant extinctions in the North American region. The K/T boundary interval was investigated as preserved on the banks of the Brazos River, Texas. The K/T fireball and ejecta layers with associated geochemical anomalies were found interbedded with this sequence which apparently allows a temporal resolution 4 orders of magnitude greater than typical K/T boundary sections. A literature search reveals that such coarse deposits are widely preserved at the K/T boundary. Impact wave deposits have not been found elsewhere on the globe, suggesting the impact occurred between North and South America. The coarse deposits preserved in Deep Sea Drilling Project (DSDP) holes 151-3 suggest the impact occurred nearby. Subsequent tectonism has complicated the picture

    Provenance of the K/T boundary layers

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    An array of chemical, physical and isotopic evidence indicates that an impact into oceanic crust terminated the Cretaceous Period. Approximately 1500 cu km of debris, dispersed by the impact fireball, fell out globally in marine and nonmarine environments producing a 2 to 4 mm thick layer (fireball layer). In North American locales, the fireball layer overlies a 15 to 25 mm thick layer of similar but distinct composition. This 15 to 25 mm layer (ejecta layer) may represent approximately 1000 cu km of lower energy ejecta from a nearby impact site. Isotopic and chemical evidence supports a mantle provenance for the bulk of the layers. The extraordinary REE pattern of the boundary clays was modelled as a mixture of oceanic crust, mantle, and approximately 10 percent continental material. The results are presented. If the siderophiles of the ejecta layer were derived solely from the mantle, a test may be available to see if the siderophile element anomaly of the fireball layer had an extraterrestrial origin. Radiogenic Os-187 is depleted in the mantle relative to an undifferentiated chondritic source. Os-187/Os-186 ratios of 1.049 and 1.108 were calculated for the ejecta and fireball layers, respectively

    ‘Thank You Howard For the Experience’

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    A Program for the Training of Elementary Art-Music Teachers

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    The writer has had experience as a supervisor of music at the elementary and secondary levels. This experience combined with the development of courses to suit the program for an elementary teacher training institution provided the background for the development of this project. The problem, as it appeared to the writer, was that in spite of valiant efforts on the part of music supervisors and art teachers’ elementary students did not comprehend music or art as an aesthetic whole. The methods in use, in most Maine schools, presented the arts as a technical skill to be mastered by the student rather than as a fine art to be first understood and then, in later grades, mastered. Investigation showed that some institutions of higher learning were combining the arts in college programs. Further search indicated an attempt on the part of some secondary and junior high teachers to combine the arts in their teaching. No evidence could be found however, that there was any effort to prepare teachers to deal with this concept at the elementary level. It seemed that this combining of the arts in the elementary grades was the most desirable approach. With this premise as a base the program of preparing an allied arts teacher for elementary grades was developed. Methods and Procedures A survey of the offerings in the area of fine arts was made by studying programs in seventy colleges and universities engaged in teacher preparation. The Music Educators National Conference publications were reviewed to determine what research had been done in the area of that combined arts. Letters were written to members of the National Association for the Humanities in Education to determine what work was being done in the field. Correspondence, review of research, and personal interviews with educators and administrators provided the direction for the study. A survey of the fifty state departments of education which resulted in forty replies pointed up the need for such a teacher preparation program. When the need for the program had been established writer proceeded to collect a bibliography that included music education, art education and general education as well as philosophical observations on the fine arts. The organization and collection of this material was accomplished in the period of two years. Summary The program was presented to the administration, Academic Affairs Committee, Faculty Council and the Dean of Academic Affairs of the University of Maine, Fort Kent, in November of 1970. With full campus approval and on the basis of the surveys the program was presented to the University Chancellor early in 1971. In March 1971 the Chancellor approved the program and the University of Maine board of trustees, at their April meeting, endorsed the course of studies for the Fort Kent campus. The program was put into operation in the fall semester of 1971 and has some eleven students involved in all or part of the allied arts concentration

    Discovery of orbital decay in SMC X-1

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    The results are reported of three observations of the binary X ray pulsar SMC X-1 with the Ginga satellite. Timing analyses of the 0.71 s X ray pulsations yield Doppler delay curves which, in turn, provide the most accurate determination of the SMC X-1 orbital parameters available to date. The orbital phase of the 3.9 day orbit is determined in May 1987, Aug. 1988, and Aug. 1988 with accuracies of 11, 1, and 3.5 s, respectively. These phases are combined with two previous determinations of the orbital phase to yield the rate of change in the orbital period: P sub orb/P sub orb = (-3.34 + or - 0.023) x 10(exp -6)/yr. An interpretation of this measurement and the known decay rate for the orbit of Cen X-3 is made in the context of tidal evolution. Finally, a discussion is presented of the relation among the stellar evolution, orbital decay, and neutron star spinup time scales for the SMC X-1 system

    Range safety signal propagation through the SRM exhaust plume of the space shuttle

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    Theoretical predictions of plume interference for the space shuttle range safety system by solid rocket booster exhaust plumes are reported. The signal propagation was calculated using a split operator technique based upon the Fresnel-Kirchoff integral, using fast Fourier transforms to evaluate the convolution and treating the plume as a series of absorbing and phase-changing screens. Talanov's lens transformation was applied to reduce aliasing problems caused by ray divergence
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